nimble/ll: Fix regression in network privacy when initiating
nimble/ll: Fix regression in network privacy when initiating

We should not connect to peer in network privacy mode only if peer
IRK is non-zero.

Fix regression introduced in fix for LL/CON/INI/BV-24-C qualification
test case.

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble